This research proposal will utilize the cell differentiation system leading to dormant spore formation in Bacillus subtilis in an investigation of the basic control of cellular differentiation. Bacteriophage 029-host cell relationship will be used as a probe for investigation of cellular alteration which occurs during spore formation. Detailed analysis of gene expression in infected host cells during cell development will be performed by use of well defined DNA fragments of the 029 genome. The alteration of membrane biosynthesis during cell development will also be studied. In addition, membranes isolated from mutants blocked in different stages of differentiation will be characterized. These studies are aimed at elucidating the nature of the genetic control of biochemical functions during cellular differentiation.